Loans - Narrative (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) Contract loan application	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for order of valuations (at least)	18 months
Troubled debt restructured loans, balance	$ 3,764,000	$ 3,933,000
Number of loans which has periodic late payments | Contract	1
Financing Receivable, Modifications, Subsequent Default, Number of Contracts with Active Forbearance Agreements	0
Consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process	$ 506,000		$ 391,000
Recognized loan fee income	$ 17,798,000	19,035,000
Residential mortgage and commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due to discontinue accrual interest on financing receivable	90 days
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for write-off of financing receivable (no later than)	120 days
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of financing receivable, updated valuation on real estate secured loans (number of days past due)	90 days
Number of previous months with no updated valuation completed for corporation to update valuation	12 months
Impaired financing receivable, valuation on real estate collateralized loans (number of days after the loan is classified as impaired)	30 days
CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructured loans, balance	$ 23,720,360
Number of loans with temporary modifications | loan	30
Number of applications | application	2,049
Total amount under PPP (up to)	$ 213,977,091
Projected fee income	8,700,000
Recognized loan fee income	953,000		$ 2,800,000
CARES Act | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructured loans, balance	$ 157,609
Number of loans with temporary modifications | loan	2
Maximum | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable term	20 years
Loan-to-value ratio (no greater than)	80.00%
Maximum | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable term	30 years
Loan-to-value ratio (no greater than)	80.00%
Loan-to-value ratio that requires private mortgage insurance (in excess of)	80.00%
Maximum | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable term	20 years
Loan-to-value ratio (no greater than)	90.00%
Nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructured loans, balance	$ 111,000	175,000
Accrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructured loans, balance	$ 3,653,000	$ 3,758,000